I out 265/65/17 on mine. yes it does fill the guards a bit more, the speed reads correctly now maybe 1-2 km over according to my GPS.
The fuel use has gone up a bit to, i now average about 550 km to a tank.
It does bog down a little but i think that is due to the manifold being blocked from a non blanked EGR system and 65,000 km on the clock.